Effects of lutein, lycopene, annatto, and gamma-tocopherol on autoxidation of triglycerides

The effects of lycopene, lutein, annatto, and gamma-tocopherol were examined on autoxidized triglycerides. Oxidation was followed by measuring hydroperoxide formation as peroxide value. The loss of the orange color of carotenoids was followed spectrophotometrically. Lutein and lycopene were prooxidants, whereas the natural food color annatto and gamma-tocopherol effectively inhibited hydroperoxide formation. By adding gamma-tocopherol, the prooxidant effect of carotenoids was inhibited and loss of yellow carotenoid color was retarded. Moreover, a combination of lutein and gamma-tocopherol was more efficient than gamma-tocopherol in inhibiting the hydroperoxide formation of triglycerides. The benefit of a combination of a carotenoid and tocopherol as an antioxidant may be due to the effect of gamma-tocopherol to retard the formation of degradation products of the carotenoid. The results suggest that potential prooxidant effects of carotenoids should be considered when carotenoids are proposed for color in lipid-containing foods.